function fecg = filter_ecg(ecg, Fs)
    Fn = Fs/2;   % Nyquist Frequency
    n = 8;
    Wn = 22 / Fn;
    [b, a] = butter(n,Wn);

%     freqz(b, a, Fn, 500);
%     title(sprintf('n = %d Butterworth Lavpas Filter',n));
%     text(28, 0, '\leftarrow Cut-off (22Hz)')

    fecg = filtfilt(b, a, ecg);
end